Provided below are ELISA kits targeting X-linked Kx blood group, a human protein encoded by XK. This protein is 444 amino acids long, with a mass of 50.9 kDa, and is a member of the XK family. This is reported to be a membrane protein. There is a noted implication in McLeod syndrome. Other alias names for this protein include: membrane transport protein XK, Kell blood group precursor (McLeod phenotype), Kx antigen, Kx blood group antigen, XK-related protein 1, kell complex 37 kDa component, and truncated X-linked Kx blood group.